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Identification and evaluation of traffic congestion are critical for better management of urban traffic, especially at merge sections where two different traffic streams converge and generate shockwaves. This study evaluates the travel time reliability measure (travel time index (TTI)) as a reliable congestion measure by analysing the impact of traffic flow parameters such as traffic volume, capacity, road geometrics and conflicting traffic flows at merge sections on TTI under mixed traffic conditions. The data required for congestion analysis were collected through video recording. Statistical models were developed to: (a) evaluate the relationship between road geometric characteristics and capacity of merge sections; (b) estimate traffic density and its evolution with time and compare it against occupancy values; and (c) correlate the relationship between TTI and traffic behaviour at merge sections and determine the variations in TTI for different levels of service of merge sections. The models developed are statistically validated using secondary data sets from the same study section, as well as from data collected from other multi-lane merge sections. The developed model successfully estimated recurring congestion by considering both space and time. This study highlights the potential usage of TTIs in capturing travel time variations more accurately at merge sections under mixed traffic conditions. [ABSTRACT FROM AUTHOR]

The great increase in car ownership has led to the daily recurrence of traffic congestion. Thus, traffic mobility, safety and emission concerns have become the most serious challenges for transportation researchers. To mitigate traffic congestion, a variety of proactive traffic-control strategies, such as ramp metering (RM), have been intensively investigated and deployed. With the aim of improving freeway traffic conditions, RM regulates the on-ramp flows dynamically in response to dynamic road conditions. However, most early RM strategies focus on optimising the traffic from one single aspect. This paper presents an RM control algorithm that predicts and evaluates the RM-controlled future traffic states. The impact of RM control was evaluated using a macroscopic traffic-flow model. The designed RM control algorithm possesses a multi-objective optimisation module, which improves the traffic network from the aspects of mobility, safety and emissions. The designed algorithm is evaluated through simulation and calibrated using field data collected over an 11 km major freeway stretch in Edmonton, Alberta, Canada. The comparison of the proposed algorithm-controlled scenario and the uncontrolled scenario shows that the proposed RM control algorithm can effectively relieve traffic congestion, improve safety and reduce carbon emissions concurrently. [ABSTRACT FROM AUTHOR]

Road pricing is an efficient instrument to regulate use of roads. In Budapest, Hungary, only cordon pricing has been investigated in detail. This paper reports on a study of the implications of applying different road pricing schemes in the city using a macroscopic traffic model. Firstly, the functional relationship between pricing schemes and road transport demand was investigated. Secondly, the implications of applying road pricing schemes on travel demand, travel time, delay time, average speed and carbon dioxide emissions of road users inside and outside of the pricing area, as well as revenues generated by applying the schemes, were studied. The results revealed that a time-based system showed the best performance inside the pricing area. However, it generated heavy congestion on non-priced roads bordering the pricing area, which would increase travel times, delay times and carbon dioxide emissions and would decrease average travel speeds on the entire network. The cordon-based system was the least effective pricing system for most of the studied parameters, while the distance-based system showed good performance both inside and outside the pricing area. Regarding the revenues generated, variable-toll systems (time-based and distance-based systems) showed the potential to generate higher revenues than the fixed-toll system (cordon-based system). [ABSTRACT FROM AUTHOR]

Designing efficient traffic signal controllers has always been an important concern in traffic engineering. This is owing to the complex and uncertain nature of traffic environments. Within such a context, reinforcement learning has been one of the most successful methods owing to its adaptability and its online learning ability. Reinforcement learning provides traffic signals with the ability automatically to determine the ideal behaviour for achieving their objective (alleviating traffic congestion). In fact, traffic signals based on reinforcement learning are able to learn and react flexibly to different traffic situations without the need of a predefined model of the environment. In this research, the actor–critic method is used for adaptive traffic signal control (ATSC-AC). Actor–critic has the advantages of both actor-only and critic-only methods. One of the most important issues in reinforcement learning is the trade-off between exploration of the traffic environment and exploitation of the knowledge already obtained. In order to tackle this challenge, two direct exploration methods are adapted to traffic signal control and compared with two indirect exploration methods. The results reveal that ATSC-ACs based on direct exploration methods have the best performance and they consistently outperform a fixed-time controller, reducing average travel time by 21%. [ABSTRACT FROM AUTHOR]

Traffic-state estimation is a key component of an advanced traffic management system. The Eulerian traffic-state estimation based on an X-T traffic-flow model has proved successful in processing traditional X-T data sources such as inductive loop data. However, over the past decade, the emergence of probe vehicle data from paired sensors has created challenges for X-T traffic-state estimation. The vehicle–space (N-X) model has shown potential benefits in modelling paired-probe data. In this paper, an original N-X traffic-state estimation framework is proposed and validated by numerical experiments. In addition, an original first-order conservation formulation is derived to address the entry and exit slip road issue for motorway corridors. An evaluation is conducted by comparing the proposed N-X estimation with the X-T estimation. The results show that the proposed model is superior to the X-T estimation in terms of accuracy and efficiency. It performs well, particularly during congestion, and can track traffic breakdowns and recoveries effectively. [ABSTRACT FROM AUTHOR]

The objective of this study is to examine travel time reliability under the heterogeneous traffic conditions prevailing in developing countries such as India. The study is carried out using a motorised two-wheeler, which is a dominant vehicular type in conditions such as are found in India on urban arterial roads. Eight runs are conducted during morning peak hours by driving a motorised two-wheeler mounted with a performance box (equipped with high-precision global positioning system) with the traffic stream on the test route between Athwa and Piplod, in Surat city, Gujarat, situated in the western part of India. One of the major outcomes of the study is to propose the most suitable relationships between buffer time index (BTI) and volume-demand-to-capacity (V/C) ratio, as well as between planning time index (PTI) and V/C ratio. From the results, it is found that a polynomial function-based model can predict BTI as well as PTI for the given V/C ratio more accurately. The study also highlights the development of a methodology to define the level of service of a roadway facility based on travel time reliability measures. Furthermore, this research work discusses potential reliability measures for capturing travel time variations more appropriately. [ABSTRACT FROM AUTHOR]

Drivers often undertake tactical and safety-related lane-changing (LC) behaviours to minimise their driving effort and travel times under different and complex traffic circumstances. LC behaviour can be affected by various factors such as lane configurations, driver characteristics, pavement surface properties and so on. Pavement surface deformations represent one such factor that forces drivers to change lane. Road surface deformations generally makes driving more difficult and they cause an increase in vehicle operation and maintenance costs. Additionally, they cause many problems, such as traffic congestion and accidents. In this study, the aim is to investigate and explain the effects of pavement surface deformations and other parameters on the LC behaviour of drivers. This study constitutes descriptive research, which uses a logit regression model (LRM) to determine the LC behaviour of drivers. The data set was collected from two different cities (Izmir and Erzurum) and four different deformed road zones in Turkey. It was found that pavement surface deformations have a high impact on the LC behaviour of drivers, and passenger cars are the vehicle type that is most affected by surface deformations. Numerical tests showed that the proposed LRM performs reasonably well in terms of the statistical relationship between LC and effective parameters. [ABSTRACT FROM AUTHOR]

Contemporary traffic engineering relies on effective management of transportation infrastructure to supply the variable mobility demands. Urban arterial congestion is a recurring problem that affects urban traffic flow. The degree of congestion may amplify if the arterial is a principal arterial that leads to a major bridge. Bosporus Bridge, inaugurated in 1973 and renamed in July 2016 as the Martyrs Bridge, is the first of the three suspension bridges connecting the Anatolian and European sides of Istanbul, Turkey. The Martyrs Bridge, along with the recently inaugurated Eurasia Roadway Tunnel provides a direct connection between the southern districts of the Anatolian and European sides of Istanbul for roadway traffic excluding trucks. Recurring congestion observed along the 5·7 km long westbound approach arterial from the Anatolian side of Istanbul to the bridge initiated a study to investigate methods to mitigate congestion through traffic management and improved roadway parameters. A micro simulation model based on traffic data suggested the applicability of traffic speed management along the existing infrastructure to relieve congestion and provide flow stability. The micro simulation model also provided the means for parametric evaluation of the effects of heavy vehicles, lane-width values and interchange spacing on the arterial flow speed and delay. [ABSTRACT FROM AUTHOR]

A model system was developed to investigate the feasibility of an integrated transportation demand management (TDM) programme in the Nanhai district of China by employing the multi-nomial logit and nested logit modelling methods. Using the model system, the impacts of the programme concerning residents' acceptance and behaviour adjustments in trip frequency, mode choice, departure time and route choice are predicted. The study results indicate that the programme could make a significant contribution to the improvement of traffic conditions in Nanhai. Furthermore, it is recommended that implementation of the integrated TDM programme in Nanhai be divided into two stages - stage 1 for the implementation of bus priority and motorcycle restriction policies and stage 2 for implementing a congestion pricing policy. The study results may facilitate the establishment of related TDM programmes to aid the mitigation of traffic congestion and the sustainable development of urban transportation systems. [ABSTRACT FROM AUTHOR]

The earliest involvement of the City Council of Tehran, Iran, in public transport was in 1919 when a Belgian company was awarded a contract to lay rail tracks in five of the streets in the city for horse-driven wagons. The population of Tehran was well under 500 000 and the city was small. Before that period the public transport had consisted of a few horses and carriages run by individuals. Now Metropolitan Tehran reaches over an area of approximately 1500 km with a population of over 12 million. The city authorities are faced with extreme motor traffic congestion, causing delays, wastage of time and an acute health hazard from pollution. The city authorities are deeply involved in efforts to reduce the traffic congestion. The objective of this paper is to assess how the Tehran Traffic Authority is proceeding with the management of the problem of traffic congestion and the effects of a number of technical measures which have been implemented. [ABSTRACT FROM AUTHOR]

The origins of a road user charging concept for central London and the development of the central London congestion charging scheme are outlined. The paper then explains the objectives and the main features of Transport for London's programme of impacts monitoring of the scheme. It summarises the main results that were obtained. Drawing on the extensive data from the monitoring programme, the paper then compares the patterns of congestion and traffic flows that were observed in the original scheme and in its western extension. This shows how congestion was initially eased as traffic levels were reduced and how it subsequently increased as the effective capacity of the road network was reduced or reallocated. The paper concludes with some reflections on the achievements of the charging scheme. [ABSTRACT FROM AUTHOR]

A technically and economically feasible road user charging scheme should be based on quantities that are readily and accurately measurable, as well as being directly variable with the amount of road use and its impact on the environment and society. A key requirement for a pricing scheme is that the charging regime used should be easy for motorists to understand, but at the same time flexible enough for the operator to implement a wide range of policies to meet different aims. A set of variable road user charging indicators is identified herein by considering both the associated costs of a trip and the operational requirements for a feasible road pricing scheme. The study then focused on identifying a set of currently feasible technologies to measure these variables in real-time with high accuracy. Particular attention was paid to the need accurately to track vehicle movements and link these movements to geographical areas and road types, and the key pollutants and particulate matter, all of which have different potential effects that are in some cases dependent on location and time of emissions. Other issues, such as congestion measurement, are also discussed. [ABSTRACT FROM AUTHOR]

Road user charging has generated a great deal of interest as a measure to alleviate the increasing congestion in the UK. Acceptability of such schemes has proved a stumbling block. In this paper, acceptability issues associated with the London scheme, the rejected proposals for Edinburgh and a possible national scheme are summarised and linked to political and media influences. Rather than concentrate on widely discussed acceptability, the paper then focuses on the behavioural response of individuals to road user charging schemes. The aim of this paper is to examine individual travel behaviour response towards actual and potential road user charging in the UK. The behavioural response is then linked to wider travel demand management schemes, and how groups of individuals, as population segments, respond. Insights are provided for the policy-sensitive segments of the socially excluded and the business community. Discussion includes possible future developments of UK road user charging. [ABSTRACT FROM AUTHOR]

The Stockholm congestion charging trial was implemented with the aim of satisfying a number of transport policy objectives related to reducing car use in the central area of Stockholm. However, the multifaceted nature of congestion that the charges aimed to alleviate was not technically defined. The traffic impact evaluation efforts were based on survey results for chosen links without any scientific review of the dynamic character of congestion or any investigation of the statistical characteristics of the chosen congestion indicator. Neither was there any analysis of area networks nor any calculation of an overall indicator. Based on a literature review, approaches for defining congestion and a number of alternative congestion performance measures were selected. Data from the trial 'before' and 'after' surveys were used to estimate congestion levels and the accuracy of the performance measures. Specific issues and lessons regarding the quality of the data collection are discussed. Accuracy rankings are presented for different cases, concluding that some performance measures showed better reliability in all situations whereas others proved to always be less reliable. These findings are used as a basis for recommendations regarding the implementations of the congestion indicators studied. [ABSTRACT FROM AUTHOR]

The present study dealt with the evaluation of the performance of signal-controlled junctions in urban areas, which exhibit high percentages of motorcycle traffic. In particular, the movement characteristics of motorcycles and the way they interact with passenger cars were investigated both qualitatively and quantitatively. Motorcycle movement affects the movement of the rest of the traffic and this impact on the operational performance of the junction approach was depicted. First, the way motorcycles move at a signal-controlled junction approach was described. To achieve this, another type of traffic lane was introduced: the 'notional' lanes, which were defined as corridors between stationary or moving traffic in the marked lanes. Next the movement of passenger cars and motorcycles was represented through vehicle headways and passenger car units. The movement of passenger cars at an approach was analysed and the way this was affected by that of motorcycles was identified. Finally, the performance of the approach was estimated through the start lag and saturation flow values, emphasising the impact of the movement of motorcycles at the junction. [ABSTRACT FROM AUTHOR]

Road pricing is widely advocated as a response to growing traffic congestion. There are, however, a number of significant impediments to implementing a nation-wide scheme including the choice and costs of the technology, concerns about equity and public acceptability, as well as the likelihood that the reduction in congestion brought about by road pricing would be undone by induced traffic. It is suggested that an alternative to road pricing would be to provide road users with advance information about journey times, uncertainty about which is the main detriment associated with congestion, by taking advantage of current developments in in-vehicle navigation devices and real time traffic information. [ABSTRACT FROM AUTHOR]

As Dublin, Ireland becomes more congested, the option of imposing a charge for access to central Dublin at peak times has become a realistic option. This paper outlines, in brief, the history of Dublin transportation planning that has led to this point, lists the alternative number of demand management tools which potentially could be used to limit demand for private car travel to the city centre with the implementation of a congestion charge being an option which would be particularly applicable to Dublin city. Estimates of the willingness of road users in Dublin to pay such a charge are put forward. The Dublin Transportation Office's Transportation Model is used to quantify the effect of different congestion charges on car usage into Dublin city centre at peak times. Effective implementation of such a measure is only seen as taking place within the context of improved public transport services within central Dublin. [ABSTRACT FROM AUTHOR]

This paper introduces an innovative approach to evaluating the benefits of linked MOVA (Microprocessor Optimised Vehicle Actuation) using a micro-simulation modelling and programming technique. The implementation of linked MOVA at signal-controlled junctions has been found to provide more efficient junction operations by either maximising capacity or minimising delay, depending on the level of congestion. Although vehicle actuation (VA) modelling is commonly available (i.e. bus gating, standalone MOVA and SCOOT), there has been no method for assessing the operational benefits and signal settings of linked MOVA implementation. Using the programming ability within the VISSIM micro-simulation software suite, a precise assessment of the benefits of linked MOVA type VA was undertaken. The signal settings, operational parameters and 'linking' of the signal control junctions were set as part of the MOVA implementation in evaluating the operational benefits. A post-implementation evaluation study is presented in which modelled operations replicated the actual operations in line with modelling standards. The model is calibrated and validated using post-MOVA implementation surveys. The results proved a significant operational benefit. On average, delay savings of 19.7% were achieved by the implementation, together with a significant reduction in total stopped delay and number of stops. Although traffic demand remained constant for pre- and post-linked MOVA operations, a 0.5% increase in throughput was observed. Modelling proved an effective method in assessing linked MOVA operations. This technique is now available to linked MOVA users, and can be adapted to other VA-type signal operations in evaluating the coordinated operations, benefits and settings before expensive implementation is undertaken. [ABSTRACT FROM AUTHOR]

This paper presents numerical experimental results for testing a simulation-based combined dynamic traffic assignment and signal optimisation algorithm under incident conditions. The algorithm utilises a path-based signal optimisation procedure, which uses vehicle paths information from a dynamic traffic system optimal assignment model to optimise the signals. The use of vehicle path in the signal optimisation procedure makes it much easier to interact with the path-based dynamic traffic assignment models. The algorithm is implemented and tested under normal and incident conditions. The experiments consist of implementations of the solution algorithm under different congestion levels for the test networks. Some experiments, under incident conditions for the test network, were used to examine the robustness of the solution algorithm. The algorithm is shown to reach convergence in all experiments, and to result in significant improvements over the system optimal assignment solution under different congestion levels. [ABSTRACT FROM AUTHOR]

The article presents information on several research papers related to traffic engineering presented at the Institute of Civil Engineers. The paper "Transport engineering--a future paved with gold?" by T. Ridley explains that transport engineering offers a potentially rich and fulfilling career, not just financially but in terms of the holistic service that transport engineers can offer society long into the future. The paper "Congestion charging: selling the concept," by S. Ison discusses the problem of increasing urban traffic worldwide, which is leading to increasing problems of congestion and environmental degradation.

A referendum in February 2005 saw Edinburgh citizens reject a transport strategy for the city, including a proposed congestion charging scheme. The aims of the strategy were to tackle road congestion and to provide a public transport system to match the best in Europe. Congestion charging was seen by the Council as a key tool both to reduce demand for road space and to provide a revenue stream for transport investment. This paper focuses on the context for the development of the proposals, the hurdles involved in taking them forward, and the apparent contradiction between initial high levels of support for a 'radical' transport policy and eventual rejection of the proposed means of achieving those objectives. The paper postulates a number of reasons why this rejection may have occurred, based on the author's experience in the development of the scheme. [ABSTRACT FROM AUTHOR]

This paper reports work done three years ago for the Highways Agency in England to stimulate long-term thinking about how to develop and operate the strategic highway network in the UK. The effects of road traffic are becoming a critical problem throughout the world, and without some radical solutions the situation is forecast to get worse. Problems such as traffic congestion, global warming and how to achieve sustainability are politically sensitive yet require positive action. Innovative thinking is needed now to develop solutions and actions that are good for the long term. The Highways Agency in its role as network operator is responsible for managing, maintaining and improving the strategic road network in England-over 8000 km of motorways and trunk roads. In a bid to look beyond the usual 5-10 year planning cycle, the Highways Agency commissioned the Vision 2030 Project. Visioning techniques and innovative thinking were used to develop several possible scenarios and propositions for the long-term future of inter-urban transport. These transport visions have influenced the Highways Agency in developing suitable action plans to achieve the desired levels of service for users of the strategic road network, against a changing and challenging background. [ABSTRACT FROM AUTHOR]